600 1000 2000 GROSS NATIONAL PRODUCT PER CAPITA (US $) Figure 3. Relationship between infant mortality rate and GNP per capita, 1965. others will have few; but still the level of health care may be comparable or be affected more by other factors. Health expenditures must be viewed with particular caution, since the private sector is more important in some countries than in others. The World Health Organization (WHO), in particular, is steadily improving the collection and standardization of these data as well as the more difficult indices of mortality and morbidity. Other important sources of health service data are the national development plans and health plans of individual countries. At this stage, however, these plans vary greatly in detail and availability; they may or may not differ significantly from WHO data. Because of these limitations of data, only six indices are used in this paper:ding to the sources indicated. In some cases expert readers will recognize that some nonitalicized figures are census or survey data from an earlier date which may have been questioned at the time and could certainly be out of date by 1965.